Drug delivery devices, especially devices which are designed for self-administration of medicament or drug by a patient, usually have sophisticated internal mechanisms which are provided to permit setting of a dose of drug to be delivered and dispensing of the dose, for example by transferring a force from a dose button which is pressed by the user to a piston or bung within a cartridge which contains the medicament, thereby displacing the piston with respect to the inner walls of the cartridge in order to expel drug from an outlet of the cartridge.
Often, clutch mechanisms are utilized within these devices in order to couple certain elements of these devices to one another only selectively. One of these devices is disclosed in WO 2004/078239 A1. The drug delivery device utilizes a clutch which cooperates with a clicker and also has a member for resetting the clutch following dispense.